Family olfactory cues

These two examples clearly indicate the still unknown potential of various marsupial families in utilizing olfactory cues. Further research is needed to fully explore the use of olfactory communication in Australian marsupials. 

Although the mechanism for HLA-based mate choice in humans is not known, MHC-based mate choice preferences in rodents are olfactory mediated (reviewed in Alberts Ober, 1993). In humans, evidence for MHC-based olfactory recognition has recently been presented by Wedekind and colleagues (Wedekind et. al., 1995, 1997). Despite the methodological limitations of these studies (Hedrick and Loeschcke, 1996), the results are consistent with the data from rodent studies and suggest that humans may indeed use olfactory cues to discriminate between persons similar and dissimilar in the MHC. This premise has been bolstered recently by the identification of a family of olfactory receptor genes (OLF) that map within the human MHC (Fan et al., 1996), but additional studies are needed to determine whether preferences for mates with dissimilar HLA haplotypes in the Hutterites are indeed mediated by olfactory cues. 

Females (75—85 days of age) were removed from their family groups and paired with unfamiliar, unrelated, mature males (65—110 days of age). Pairs exposed to the mother (N = 19), olfactory cues from the family (N = 19), or clean bedding (N = 21) were... 

Olfactory cues alone were also not sufficient to suppress reproduction in females but a significantly smaller proportion of females produced litters if housed with a prospective mate and the mother (Figure 3). Soiled bedding from the mother = 0.047, df = 2, P = 0.977 Brant, 1995) or from the daughter s family (x = 8.07, df = 2, P = 0.0177, Brant, Schwab, Vandenbergh, Schaefer Solomon, 1998 Fig. 3) did not prevent daughters from producing litters. 

Figure 3. Percentage of daughters that produced litters when housed with an unfamiliar adult male and their mother, olfactory cues from their families, or clean bedding for up to 60 days after separation from their family. Different letters indicate statistically significant differences among treatments. Sample sizes are shown within bars. Adapted from Brant et al. (1998).

Figure 4. Time spent (hours) by weanling and mature (a) female and (b) male pine voles with olfactory cues from an unfamiliar, mature opposite-sex conspecific versus those from their family. For females, there was a significant difference between age classes (P = 0.01) but for males the effect was of borderline statistical significance (P = 0.05). Adapted from Solomon Rumbaugh (1997).

Herbivores can typically sense suitable host plants using olfactory cues from long distance. Many volatile terpenoids bear the essential information in their molecular structure. Different stereo isomers of the same compound may result in different response when sensed by insect antennae or the olfactory sensors in the nose of vertebrate animals. Another important factor affecting signal perception and behavioral response in herbivore is the relative proportion of different volatile compounds, terpenoids or other volatiles, in the odor plume released by a plant. CombinatiOTi of certain monoterpenes and sesquiterpenes are very distinctive in certain plant families. Specialist herbivore species can separate these combinations from similar monoterpenes released by other plants, because of their strict ratio in the host species. 

The probably universal occurrence of large olfactory mucosae and bulbs in three of the four procellariiform families comprising over 90% of the species compels careful behavioral study. These birds unquestionably are reacting to odors in significant ways. How does such dependence interact with reliance on visual and other sensory cues The prominence of their olfactory equipment implies some degree of functional dominance for smell. Our present understanding of olfactory mechanisms does not tell us what specific advantages reside in more, rather than less, olfactory tissue. 

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